Walking lowers breast cancer risk

Postmenopausal women who walk at least 7 hours per week have a significantly lower risk of breast cancer than their less active counterparts. Those are the findings of a large epidemiologic study published in Cancer: Epidemiology Biomarkers & Prevention.

More than 70,000 postmenopausal women aged 50 to 74 were represented in the research, 4,760 of whom were diagnosed with breast cancer between 1992 and 2009. The data are from the American Cancer Society Prevention Study II Nutrition Cohort.  

Researchers used extended Cox regression to estimate multivariable-adjusted relative risks (RR) of breast cancer in the cohort, in relation to total recreational physical activity, walking, and leisure-time sitting. They also looked at how estrogen receptor (ER) status, body mass index (BMI), weight gain, and use of postmenopausal hormones might impact RRs.

Risk of breast cancer was 25% lower in the most active women (>42 MET-hours/week physical activity) than in the least active (0 to <7 MET-hours/week; 95% CI, 0.63-0.89; P_trend = 0.01). Among the 47% of women who walked as their only recreational activity, doing so for ≥7 hours per week was associated with a 14% lower risk of breast cancer than for ≤3 hours per week (95% CI, 0.75-0.98).

None of the associations differed based on the women’s ER status, BMI, weight gain, or use of postmenopausal hormones and sitting time was not associated with risk. The study results, the authors said, support an inverse association between physical activity and postmenopausal breast cancer irrespective of the other factors. 

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